Electrical Basics

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Old 02-21-04, 09:43 PM
vashley
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Electrical Basics

I have very basic question.Whats the meaning of grounding & neautral ? why is it required. why there is three or sometimes
two pin point in plugging box. pls. give me description and
web site to know basic about electrical
 
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Old 02-21-04, 11:32 PM
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There's all kind of help for electrical basics right here on the internet.

Try this link:
 
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Old 02-23-04, 11:59 AM
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I am someone trying to learn myself and had the following questions about something from this web site jughead refered the poster to:

[QUOTE from http://www.electrical-online.com/how.../Grounding.htm]
Proper grounding provides a safe path for electricity to safely move from a defective outlet, fixture, appliance or tool back into the earth, which happens to be a very good electrical conductor. Homes are grounded by either the use of ground electrodes (ground rods) or by ground plates. Another grounding option sometimes used is the home's cold water supply pipe, providing that it is copper and is continuous to the water main. [/QUOTE]

I have some questions regarding this:

John Nelson has said the Earth is a poor conductor of electricity. Which is right?

I thought there were two grounding systems in a house. The equipment grounding and the Grounding electrode. The idea of equipment ground is if there is a some sort of fault like say a refrigerator and the hot wire is shorting against the metal case a properly grounded outlet will send the electricity from the short back through the ground to the main panel and trip the breaker.

The grounding electrode is for lightning protection.

If what I am thinking is correct then the above statment does not make any sence to me.

anyone's thoughts appreciated
 
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Old 02-23-04, 01:41 PM
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The main reason of the grounding as I understand it is that if there is a short in an outlet or appliance such as a fridge the power will take the easiest path, the ground. Otherwise if there is a short as soon as you touch the appliance and you are grounded the power will go through your body to the ground, not a good thing.

The power going back to the panel on the ground wont always trip the breaker, unless there is a dead short in which case the current is large enough to trip the breaker, but this has nothing to do with the ground coming back to the panel, only to do with the current leaving the panel.
 
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Old 02-23-04, 02:09 PM
DaveB.inVa
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Heres a good discussion that doesnt get too indepth that occured here a couple days ago. Long story short, the electrical online advice isnt too great, the earth is a poor conductor for these voltages and electricity doesnt try to go to the earth. The earth isnt a magical drain for electricity!

http://forum.doityourself.com/showth...hreadid=159781
 
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Old 02-23-04, 03:54 PM
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Albert Einstein once said that things should be made as simple as possible -- but no simpler. By suggesting that the earth is a good electrical conductor, I think the author has crossed the line.

The earth is a good electrical conductor relative to a block of wood. The earth is a poor electrical conductor relative to a copper wire. It's all in your perspective. But the important thing here is that the earth is usually not a good enough electrical conductor to trip the breaker before you die.
 
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Old 02-23-04, 05:13 PM
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Grounds

Remember a couple of basics.
1. The earth IS a conductor. All electric utilities bond their residential services to earth ground.
2. There is a GROUNDED conductor (white) and a GROUNDING conductor (bare copper).
3. For current to flow, there has to be a complete circuit (ie-the electricity has to return to its' source). In a normal circuit, the black is the source, the grounded (white) conductor is the return.

Consider any metal appliance; for example a sewing machine. In normal operation, the electric current comes in on the hot (black) wire, goes through the appliance, and returns to its source on the white wire. The frame of the appliance is connected to the GROUNDING (bare) wire and does not carry current in NORMAL circumstances.
REMEMBER, the system is grounded to earth and will take any conductive path it can to get there. If the insulation fails on the appliance and the frame becomes hot, it will be shorted to the GROUNDING conductor and trip the breaker. If the appliance is NOT grounded properly (your brother in law tore off the third prong so it would fit your old two prong receptacle), then the only path to ground is through whatever is touching the frame, usually you.

Is earth a good conductor? Yes and no. Black farmland after a week of rain is a great conductor. Sand in West Texas after 3 months of drought is practically an insulator! But the fact remains that it only takes about 5 MILLIAMPS of current through your heart to send it into fibrillation. Since a 20 amp breaker trips at approximately 20 amps, it takes 4000 times the amount of current to trip the breaker as it does to kill you.

POINT TO REMEMBER. Breakers (excluding GFI ground fault interruptors) are designed to protect the wire from thermal overload, NOT the user from electrocution.
 
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Old 02-23-04, 05:22 PM
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A basic premise of electricity is that it will flow mostly in the lowest resistance path. It is true that the earth itself is not a very good conductor relative to a copper wire. In fact, the resistance of the earth varies some depending on where you live. Maps exist detailing just what those values are for the United States. The idea of the non insulated copper ground wire is to provide an additional conductor back to the neutral in the entrance panel for safety purposes. Connecting the panel frame and the neutral itself to a copper ground rod outside acts mostly as lightening protection. If there is a short in an eletrical applicance that puts 120vac onto the case you want that case to provide the very lowest resistance path back to the neutral you can get. By doing so you accomplish two things. First you will give yourself the best chance for sufficient current to flow to trip the breaker. Secondly the amount of current flowing through your body will be kept to a minimum.

If I remember my first aid correctly, the flow of just 20 to 50 thousands of an amp through your heart is sufficient to stop it. There have been many studies done on the effect of electricity on the human body. It can make for some grim reading. A much overlooked danger of electricity is the secondary effects it may cause. Let's say you were using an electric drill (not a cordless model) while on a metal ladder. The drill shorts, you don't have it grounded, and you receive a shock. There is a better than even chance that you will fall from the ladder. The injuries you receive from the shock may be slight, but the fall most likely will break bones or even kill. It would be wise to treat anything plugged into a 120vac socket with a measure of respect because it can do you some serious damage. I can tell you that from first hand experience.
 
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